This invention relates generally to organic synthesis and more particularly to the formation of cyclic formals from negatively substituted diols and formaldehyde.
In general, the formation of acetals and formals has been accomplished through the use of acid catalysts and often times with the addition of dehydrating agents. This is done in order to remove the water formed and shift the reaction equilibrium towards continued acetal formation. Several different dehydrating agents have so been employed. Alternatively, this may be accomplished by removing the water produced by azeotropic distillation (see H. M. Flowers in The Chemistry of the Hydroxyl Group, S. Patai Ed., J. Wiley and Sons Ltd., London (1971), pg 1028).
It was found in cases where the alcohol contained electron withdrawing substituents (as with the object compound of this invention) that acetal or formal formation would proceed only under severe reaction conditions. Usually, strong acids such as concentrated sulphuric acid are used. In those instances, degree of conversion to acetal was sensitive to acid concentration, reagent concentration, and reaction temperature. As a consequence, reaction conditions must be optimized and stringently controlled (see K. G. Shipp and M. E. Hill, J. Org. Chem., 31, 853 (1966)).
Alternatively, successful formation of acetals and formals has been accomplished by means of reaction of the alkoxide with a geminal dihalide. However, product yields obtained using this procedure were generally lower than those attainable using the acid catalysis method.